Brown sausage in a skillet over medium heat, crumbling as it cooks. Stir in flour and cook 1 minute. Gradually whisk in milk.
Simmer for 5 minutes, stirring often, until thickened. Season with salt, pepper, and garlic powder. Keep warm.
Whisk eggs, milk, salt, and pepper. Melt butter in a non-stick skillet over medium heat, pour in the eggs, and stir gently until just set. Remove from heat while still soft.
Preheat oven to 375°F. Grease a 9x13-inch dish. Fill tortillas with scrambled eggs, potatoes (if using), green onions, cheddar, and Monterey Jack cheese. Roll up and place seam-side down in the dish.
Pour sausage gravy evenly over the enchiladas. Add extra cheese on top if desired.
Cover with foil and bake for 15 minutes. Uncover and bake 5–10 minutes more, until hot and bubbly.
Garnish with green onions and hot sauce. Serve with fresh fruit or juice.